16
PHO
TOMETER
7.3. CUVETTE PREPARATION
Proper mixing is very important for reproducibility of the measurements. The mixing
method is indicated with “shake gently“ using one of the following icons:
In order to avoid reagent leaking and to obtain more accurate
measurements, close the cuvette first with the supplied HDPE plastic
stopper
and then the black cap.
Whenever the cuvette is placed into the measurement holder, it must be
dry outside and free of fingerprints, oil or dirt. Wipe it thoroughly with
HI731318
or a lint‑free cloth prior to insertion.
Shaking the cuvette can generate bubbles in the sample, causing higher readings. To
obtain accurate measurements, remove such bubbles by swirling or by gently tapping
the cuvette.
Do not let the reacted sample stand too long after reagent
has been added. For best accuracy, respect the timings
described in each specific method.
It is possible to take multiple readings in a row, but it is
recommended to take a new zero reading for each sample
and to use the same cuvette for zeroing and measurement
when possible.
Discard the sample immediately after the reading has been taken, or the glass might
become permanently stained.
All the reaction times reported in this manual are at 25 °C (77 °F). In general, the
reaction time should be increased for temperatures lower than 20 °C (68 °F), and
decreased for temperatures higher than 25 °C (77 °F).
7.2.3. PROPER USE OF DROPPER BOTTLE
(a) For reproducible results, tap the dropper on the table several
times and wipe the outside of the tip
with a cloth.
(b) Always keep the dropper bottle in
a vertical position while dosing the
reagent.
